Clock Synthesizer Control Register Syncr

Freescale Semiconductor, Inc.

4.3.2.8SOFTWARE SERVICE REGISTER (SWSR). The SWSR is the location to which the software watchdog servicing sequence is written. The software watchdog can be enabled or disabled by the SWE bit in the SYPCR. SWSR can be written at any time, but returns all zeros when read.

SWSR							$027
7	6	5	4	3	2	1	0

SWSR7 SWSR6 SWSR5 SWSR4 SWSR3 SWSR2 SWSR1 SWSR0

RESET:
0	0	0	0	0	0	0	0

Supervisor Only

4.3.3 Clock Synthesizer Control Register (SYNCR)

The SYNCR can be read or written only in supervisor mode. The reset state of SYNCR produces an operating frequency of 8.39 MHz when the PLL is referenced to a 32.768- kHz reference signal. The system frequency is controlled by the frequency control bits in the upper byte of the SYNCR as follows:

FSYSTEM = FCRYSTAL [2(2+2W+X) ] ⋅ (Y+1)

SYNCR															$004
15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
W	X	Y5	Y4	Y3	Y2	Y1	Y0	RSVD	0	0	SLIMP	SLOCK	RSTEN	STSIM	STEXT
RESET:
0	0	1	1	1	1	1	1	0	0	0	U	U	0	0	0
U = Unaffected by reset													Supervisor Only

W—Frequency Control Bit

This bit controls the prescaler tap in the synthesizer feedback loop. Setting the bit increases the VCO speed by a factor of 4, requiring a time delay for the VCO to relock (see equation for determining system frequency).

X—Frequency Control Bit

This bit controls a divide-by-two prescaler, which is not in the synthesizer feedback loop. Setting the bit doubles the system clock speed without changing the VCO speed, as specified in the equation for determining system frequency; therefore, no delay is incurred to relock the VCO.

Y5–Y0—Frequency Control Bits

The Y-bits, with a value from 0–63, control the modulus downcounter in the synthesizer feedback loop, causing it to divide by the value of Y+1 (see the equation for determining system frequency). Changing these bits requires a time delay for the VCO to relock.

Bits 7–5—Reserved

Bit 7 is reserved for factory testing.

4- 28MC68340 USER’S MANUALMOTOROLA

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MC68340 specifications

The Motorola MC68340 is a highly integrated microprocessor that was introduced in the early 1990s. It belongs to the 68000 family of microprocessors and is designed to cater to the demands of embedded systems, particularly in telecommunications and networking applications. This chip represents a significant evolution in microprocessor technology by combining a microprocessor core with additional peripherals on a single chip, making it an attractive solution for engineers looking to design compact and efficient systems.

One of the key features of the MC68340 is its 32-bit architecture, which allows for significant processing power and data handling capabilities. This architecture enables the processor to handle larger data sizes and perform more complex calculations compared to its 16-bit predecessors. The MC68340 operates at clock speeds typically ranging from 16 MHz to 25 MHz. Its dual instruction pipeline enhances throughput, allowing for simultaneous instruction fetches and executions, which significantly boosts performance.

A notable characteristic of the MC68340 is the inclusion of integrated peripherals, which help reduce the overall component count in a system. Key integrated components include a memory management unit (MMU), a direct memory access (DMA) controller, and various communication interfaces such as serial ports. The memory management capabilities enhance the processor's ability to manage memory resources efficiently, enabling it to support multitasking environments commonly found in modern computing.

In terms of connectivity, the MC68340 features connections for both synchronous and asynchronous serial communication, making it well-suited for networking tasks. The processor supports a range of bus standards, including address and data buses, which facilitate seamless interaction with peripheral devices.

Another important aspect of the MC68340 is its flexibility. The processor supports multiple operating modes, including multiple CPU configurations and compatibility with the Motorola 68000 family, allowing for easier integration into existing systems.

Moreover, the MC68340 boasts low power consumption compared to many of its contemporaries, making it an excellent choice for battery-operated applications, enhancing its appeal in sectors like telecommunications, industrial control, and automotive systems. Its combination of performance, integration, versatility, and efficiency has secured the MC68340 a reputable position in the annals of embedded systems technology, proving to be a valuable asset for developers and engineers alike.

Motorola MC68340 manual Clock Synthesizer Control Register Syncr

Models: MC68340

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

4.3.3 Clock Synthesizer Control Register (SYNCR)

SYNCR

MC68340 specifications